1. Field of the Invention
The present invention relates to an inrush voltage clamping circuit and related chip, and more particularly, to an inrush voltage clamping circuit for clamping inrush voltage induced by hot plugs and related chip.
2. Description of the Prior Art
In general, operating power of a chip is provided by external power supplies. Please refer to FIG. 1. FIG. 1 is a schematic diagram illustrating a hot plug equivalent circuit of a chip 100 in the prior art. A power supply 102 provides power into an input power end 104 of the chip 100. As shown in FIG. 1, when the power is provided to the input power end 104 instantaneously, an inrush voltage is occurs due to an RLC circuit having a line inductor Lwire, a line resistor Rwire, and a power capacitor CVCC. The inrush voltage may result in an over-voltage effect, reducing reliability of the integrated circuit and its life time, even causing the chip 100 to breakdown, damaging the integrated circuit of the chip 100 or an external device.
In order to improve the above-mentioned problem, the prior art provides several methods. Please refer to FIG. 2 and FIG. 3. In FIG. 2, an equivalent series resistor RCVCC is added to the power capacitor CVCC in order to reduce the inrush voltage peak. In FIG. 3, a Zener diode is used for clamping voltage peaks, and is coupled between the input power end 104 and a ground end. However, the prior art decreases the inrush voltage peak, but at the cost of increasing circuit complexity and reduced circuit performance. For example, by using the method shown in FIG. 2, the equivalent series resistor RCVCC of the power capacitor CVCC introduces power noise in normal operation. Also, the method only reduces the inrush voltage, without clamping the inrush voltage effectively. Thus, the prior art spends more manufacturing cost and more printed circuit board area for solving the above-mentioned problem.